Gnats Common after Rains

Non-biting gnats or midges (Figure 1) are common names for several species of small, non-biting flies that can breed in accumulations of standing water, ponds, or lakes; the same types of situations that can produce mosquitoes. They cannot bite or feed and individuals live for only a few days. However, emergence can occur over a long time, causing a chronic problem, especially during wet periods. Large numbers can emerge and become severe nuisances. These gnats are not strong fliers so their flight range is limited, but they can be aided by winds. They are attracted to lights so many can collect on or around houses and buildings.

Figure 1. Non-biting gnats can be a “gnuisance” (Photo: Lee Townsend, UK).

Sites that Encourage Gnat Development

There are many potential sources of gnats around a landscape or community. The larvae or immature stages of some species develop in wet soils and seepage areas with lots of organic matter; others can develop in ponds or lakes. Fortunately, most sites will dry up and not be suitable for gnats in a few days, but species that develop in permanent bodies of water can be a chronic problem.

Gnat Life Cycle

The life cycle of these insects (egg, larva, pupa, and adult) can take just a few day or several weeks, depending on the species. There can be several generations during the year. The larvae develop in wet areas or standing water where they feed on suspended organic matter or muck on pond bottoms. Stagnant water makes an ideal breeding site because of all of the microorganisms present that serve as food.

Management Difficulties

Gnats are a difficult problem to control with insecticides because of the lack of treatments available for aquatic sites where they breed.  Not only are there potential environmental impacts from applying insecticides to water, but many gnats live in the bottom muck of ponds that are difficult to treat with the few products that are available.


By Lee Townsend, Extension Entomologist


Posted in Human Pests